Cam cleats that are used to secure lines or ropes, particularly in sailing craft, are well known in the art. Such cleats generally comprise two opposed and pivoted cam-shaped blocks with arcuate toothed surfaces for gripping the ropes. The toothed surfaces generally are at right angles to the axis of the rope to be engaged. The cam blocks are spring-loaded toward a normally closed position. The toothed cam surfaces are non-concentric with respect to their pivot axes. This non-concentricity results in an increasing distance between the cam surfaces as the cam blocks are opened on their pivot axes.
In operation, such cam cleats most generally are used to engage a rope, sheet, or line while it is under tension. The rope bears laterally against the cam surfaces at the juncture between the cams, and a backward/downward pull on the rope tends to force the cams apart against the spring-loading of the cam blocks. When the cam blocks have opened sufficiently to allow entry of the rope, it must be forced downwardly between the cam teeth. When opposing tension on the free end of the rope is released, the sides of the rope are engaged by the teeth on the cam blocks. The forward pull on the rope tends to close the cam blocks by drag on the teeth, thereby increasing the pinching action of the cam teeth on the rope. To release the rope or sheet, its free end is pulled backwardly to release the pinching or gripping action of the cams, and then the rope is raised upwardly out from between the cleat teeth.
A serious disadvantage of present cam cleats is that they rapidly chafe the rope or line, primarily during entry of the rope into the cleat (cleating) or release from the cleat. This is due to the fact that the teeth faces generally are vertical to the plane of the cleat base, or are slanted backwardly from bottom to top to hold the rope while it is in the cleat. Thus, upon entry or release, the transverse motion of the rope against the relatively sharp edges of the cleat teeth performs a diagonal cutting action on rope fibers. This is particularly the case during release when the rope is under full tension; it is stretched its thinnest, and the person releasing the rope has to pull against the forward pull on the rope to open the cam enough to permit release. In more advanced cleats there are flared ears on the upper surfaces with heavy teeth that provide lead-ins for use during cleating of the rope. Again, in this type of cleat, a diagonal cutting drag is experienced during the cleating procedure as well as during uncleating.
Further, cam cleats of the general type have a limited range of rope diameters that can be accommodated. This range or diameter depends primarily on the degree of concentricity of the arcuate surfaces with respect to their pivot axes. In general, the more concentric the cam surfaces are, the less the maximum distance between the cams when fully opened; but a greater surface area is presented for gripping the rope. Thus any cam cleat design represents a compromise between the holding force desired and the size of the ropes held. For ropes having diameters close to the maximum cam cleat opening, the cutting and abrasion action of the present designs of cleat teeth are severe.
Cleats of the general type are exemplified by the patents to Weil, U.S. Pat. No. 3,051,116; to Hume, U.S. Pat. No. 3,265,032; to Helms, U.S. Pat. No. 3,730,129; to Nash, U.S. Pat. No. 3,756,061; to Merry, U.S. Pat. No. 3,795,218; and to Feder, U.S. Pat. No. 4,084,532. Each of these patents shows a cam cleat of the general type involved and some including the patents to Hume, Helms, Merry and Feder have tapered and toothed rope entry surfaces on the upper edges of the cams to help lever open the cams against the biasing-closed spring force. In these four latter patents, the rope engaging teeth are at right angles to both the longitudinal axis of the rope to be engaged and the baseplate. Nash has teeth that are slightly canted from a vertical plane normal to the axis of the rope, but are tilted or raked backwardly completely from bottom to top as in some conventional jam cleats. Nash does not have tapered entry surfaces. In addition, the slanted surfaces on the teeth of Nash are oriented to effectively resist or deflect the rope away from the rope-engaging teeth. Feder has tapered entry teeth, but the teeth on his entry surfaces are tilted or raked in a direction opposite that contemplated in the present invention, and accordingly work against cam opening and resist easy cleating. Feder's rope gripping teeth are normal to the baseplate. Feder's "teeth" surfaces are multi-plane shapes terminating in planar ridges contacting the rope surface rather than teeth that "bite" into the rope.
Jam cleats are fixed jaw cleats that are tapered in a V-shape from top to bottom. These cleats also have teeth slanted forward from top to bottom to grip the rope. The abrasion and cutting of rope fibers is at least equally, if not more severe in jam cleats than cam cleats because the jaws do not open upon backward pull of the rope to release it. In order to minimize wear on the rope, typical teeth edges are smoothed or rounded, but this sacrifices gripping of the rope. To compensate for slippage, teeth are over-slanted at acute backward angles, a poor compromise, at best.
Sliding jaw cleats are also well known in the art as exemplified in patents to Keelyn, U.S. Pat. No. 332,347; to Cope, U.S. Pat. No. 482,975; to Lowry et al, U.S. Pat. No. 824,556; and to Entwistle et al, U.S. Pat. No. 1,720,037. In such cleats the jaws are usually mounted on slides angled toward each other to provide a decreasing nip as the jaws move forward. Typically such cleats have teeth slanted backward (from bottom to top), or cross-hatched roughened surfaces, or rope conforming surfaces.
Accordingly, there is a need for improved cleat teeth structures adaptable for use in fixed or movable jaw cleats, particularly of the jam, cam or wedge action type cleats, which provide excellent grip on the wire of fiber rope, yet which have improved entry or opening means and permit entry and removal with lessened rope wear.